diff --git a/src/boards/273.c b/src/boards/273.c
new file mode 100644
index 0000000..5310d1f
--- /dev/null
+++ b/src/boards/273.c
@@ -0,0 +1,83 @@
+/* FCE Ultra - NES/Famicom Emulator
+ *
+ * Copyright notice for this file:
+ *  Copyright (C) 2025 NewRisingSun
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "mapinc.h"
+#include "asic_vrc2and4.h"
+
+static uint8 irqEnabled;
+static uint8 irqCounter;
+static uint8 irqPrescaler;
+static uint8 irqMask;
+
+static SFORMAT stateRegs[] ={
+	{ &irqEnabled, 1, "IRQE" },
+	{ &irqCounter, 1, "CNTR" },
+	{ &irqPrescaler, 1, "IRQP" },
+	{ &irqMask, 1, "IRQM" },
+	{ 0 }
+};
+
+static void sync () {
+	VRC24_syncPRG(0x01F, 0x000);
+	VRC24_syncCHR(0x1FF, 0x000);
+	VRC24_syncMirror();
+}
+
+static DECLFW(writeIRQ) {
+	switch(A &8) {
+		case 0:
+			irqCounter = V;
+			X6502_IRQEnd(FCEU_IQEXT);
+			break;
+		case 8:
+			irqEnabled = V;
+			if (~irqEnabled &1) {
+				irqPrescaler = 0;
+				irqMask = 0x7F;
+				X6502_IRQEnd(FCEU_IQEXT);
+			}
+			break;
+	}
+}
+
+static void FP_FASTAPASS(1) cpuCycle (int a) {
+	while (a--) {
+		if (irqEnabled &1 && !(++irqPrescaler &irqMask)) {
+			irqMask = 0xFF;
+			if (!++irqCounter)
+				X6502_IRQBegin(FCEU_IQEXT);
+			else
+				X6502_IRQEnd(FCEU_IQEXT);
+		}
+	}
+}
+
+static void power(void) {
+	irqEnabled = irqCounter = irqPrescaler = irqMask = 0;
+	VRC24_power();
+	SetWriteHandler(0xF000, 0xFFFF, writeIRQ);
+}
+
+void Mapper273_Init (CartInfo *info) {
+	VRC2_init(info, sync, 0x04, 0x08, NULL, NULL, NULL, NULL);
+	AddExState(stateRegs, ~0, 0, 0);
+	info->Power = power;
+	MapIRQHook = cpuCycle;
+}
diff --git a/src/boards/565.c b/src/boards/565.c
index 76ccfde..722cf17 100644
--- a/src/boards/565.c
+++ b/src/boards/565.c
@@ -24,13 +24,11 @@
 static uint8 irqEnabled;
 static uint8 irqCounter;
 static uint8 irqPrescaler;
-static uint8 irqMask;
 
 static SFORMAT stateRegs[] ={
 	{ &irqEnabled, 1, "IRQE" },
-	{ &irqCounter, 1, "CNTL" },
+	{ &irqCounter, 1, "CNTR" },
 	{ &irqPrescaler, 1, "IRQP" },
-	{ &irqMask, 1, "IRQC" },
 	{ 0 }
 };
 
@@ -53,7 +51,7 @@ static DECLFW(writeIRQ) {
 	}
 }
 
-void FP_FASTAPASS(1) cpuCycle (int a) {
+static void FP_FASTAPASS(1) cpuCycle (int a) {
 	while (a--) {
 		if (irqEnabled &1) {
 			irqPrescaler++;
@@ -67,7 +65,7 @@ void FP_FASTAPASS(1) cpuCycle (int a) {
 }
 
 static void power(void) {
-	irqEnabled = irqCounter = irqPrescaler = irqMask = 0;
+	irqEnabled = irqCounter = irqPrescaler = 0;
 	VRC24_power();
 	SetWriteHandler(0xF000, 0xFFFF, writeIRQ);
 }
diff --git a/src/ines.c b/src/ines.c
index fe5448a..3acaa15 100644
--- a/src/ines.c
+++ b/src/ines.c
@@ -728,6 +728,7 @@ INES_BOARD_BEGIN()
 	INES_BOARD( "OneBus+412C Bankswitch",   270, Mapper270_Init         )
 	INES_BOARD( "MGC-026",                  271, Mapper271_Init         )
 	INES_BOARD( "Akumajō Special: Boku Dracula-kun", 272, Mapper272_Init         )
+	INES_BOARD( "J-3?-C",                   273, Mapper273_Init         )
 	INES_BOARD( "80013-B",                  274, BMC80013B_Init         )
 	INES_BOARD( "",                         277, Mapper277_Init         )
 	INES_BOARD( "K-3017",                   280, Mapper280_Init         )
diff --git a/src/ines.h b/src/ines.h
index bcaff87..5024027 100644
--- a/src/ines.h
+++ b/src/ines.h
@@ -254,6 +254,7 @@ void Mapper255_Init(CartInfo *);
 void GN45_Init(CartInfo *info); /* m361, m366 */
 void Mapper270_Init(CartInfo *);
 void Mapper272_Init(CartInfo *);
+void Mapper273_Init(CartInfo *);
 void Mapper277_Init(CartInfo *);
 void Mapper280_Init(CartInfo *);
 void Mapper281_Init(CartInfo *);